The present invention relates to a molded assembly and a method for producing a molded assembly. The molded assembly includes an applique or face panel which is in-molded in an injection molded process.
Switches, lamps, and other devices which are used as indicators, controls or displays are an essential component of many appliances and devices. It is often an important design consideration that such devices be efficiently and inexpensively produced with a high degree of reliability and to provide ease of assembly or integration into the particular device or appliance. Further reference will be made to switches although it should be understood that the discussion of devices is intended to be interpreted broadly and to include such devices as displays, indicator lamps and other such devices.
An example of switches used with an appliance may be found on a number of devices either in the office or at home. Such devices may include industrial machines, computers, photo copiers, household appliances such as microwave ovens, stoves, washing machines and dryers. These switches are by no means limited to stationary equipment but may also be found on vehicles such as automobiles, boats, jettskis as well as other devices including exercise equipment and vending equipment.
As a practical matter, it is desirable to assure that the devices such as switches will operate reliably for a sufficiently long product life. This of course may depend on the type of application. It is also desirable to provide a switch which is easy to maintain regardless of the environment in which it operates. This is an especially important consideration in such environments as industrial environments, home environments such as the kitchen, as well as high use areas such as vending equipment and exercise equipment.
A number of prior art switches are available which are discreet components which plug into or connect to a switch panel. These discreet components often project though an opening in the panel with the body or the mechanical components of the switch being positioned behind the panel. While this type of switch is feasible for some applications, many applications require an integrated switch. An integrated switch is integrated into the surface of the control panel thereby eliminating an opening through the panel surface. The elimination of the opening through the panel surface improves maintainability and reliability by preventing the buildup of material in the switch which may enter the switch though the opening in the panel.
In response to the need for an integrated switch, a number of electro mechanical or solid state switches have been devised. One form of switch is a "dome" switch. The dome switch includes a surface membrane which provides graphical representations of switches and appropriate indicia or text identifying the switch or various switch conditions. A domed structure is positioned behind the membrane and a mechanical component of the switch is positioned behind the dome. This type of dome switch provides a barrier between the operator and the switch components thereby improving the reliability of the switch. This type of switch, however, has a problem in that after numerous actuations, the dome portion of the switch may fail thereby requiring replacement of the switch. Therefore, it would be desirable to provide a switch which eliminates this mechanical operating aspect.
Further developments have led to a mechanical switch which is essentially comprised of separated circuitry. Circuit paths are formed on membrane material providing the essential electrical paths for the circuit. Portions of these circuit paths are separated by a small gap thereby providing the "open" structure of a switch. When pressure is applied to the circuit material, the open portion of the switch is closed, thereby resulting in the actuation of the switch. Since the circuitry is very small and the gap between the open portion of the circuit is also very small, only a slight pressure needs to be applied to the surface of the switch panel to actuate the switch. This type of switch has the advantage in that the dome component is not required, thereby eliminating potential for mechanical failure.
Many applications of this type of "touch panel" switch can be found on home appliances such as ovens, and washing machines. A face applique is reverse printed with the control graphics and indicia to represent to the user a familiar mechanical type switch. A panel circuit including switch circuity is attached to the reverse side of the face applique which is in turn attached to the appliance by means of an appropriate adhesive. In such a touch panel, a portion of circuitry extends from the panel circuit to provide a connector between the panel circuit and the circuitry in the appliance.
A problem arises in the application of such touch panel switches in that in many environments, the panel may separate from the appliance which may result in complications or a reduction in the reliability of the touch panel control switch. For example, if a touch panel control switch assembly is attached to a washing machine, moisture from the washing machine may short out the circuitry or act on the adhesive and thereby loosen the touch panel from the appliance. Similarly, but in a different fashion, if such a touch panel control is used on an oven or dryer, the elevated temperatures produced by the appliance may result in a softening of the adhesive thereby producing a loosening or release of the panel from the appliance.
Therefore, it would be desirable to integrally mold such a touch panel into a molded assembly such that the touch panel is at least partially encapsulated in the molded assembly. Heretofore, it is unknown to Applicant that such an "in-molding" process has been successful with such touch panel control switches. A foremost problem which occurs during the in-molding process is that the molding forces tend to close or fuse the switch circuitry resulting in switch failure. During the molding process, the mold portions come together and introduce molten plastic over the touch panel assembly. The injection forces press against the panel thereby forcing the switch into a closed position. As a result of the mechanical forces and elevated temperature, the switches may become permanently deformed or even fused thereby resulting in an inoperative switch.
For the foregoing reasons, there is a need for a method and molded assembly in which a touch panel is in-molded into a molded assembly.